For example, a valve timing adjusting system is provided for an engine of a motor vehicle. An engine has induction/exhaust valves. For example, such valve timing adjusting system is provided between a crankshaft of the engine and a camshaft linked with the induction/exhaust valves, to thereby adjust opening/closing timing of the induction/exhaust valves according to an operation condition of the engine, by changing the relative rotational position of the camshaft to the crankshaft.
The valve timing adjusting system includes a vane which rotates with the camshaft and a cylindrical housing which rotates with the crankshaft. The vane is accommodated within the housing. And, the vane and the housing are designed to rotate relatively within a certain rotational angle range.
The vane has plural outwardly projecting portions, whereas the housing has plural inwardly projecting portions. And, plural hydraulic chambers are formed between an outer circumferential surface of the vane and an inner circumferential surface of the housing, so as to be partitioned alternately by the outwardly projecting portions and the inwardly projecting portions. When a hydraulic pressure is supplied to the hydraulic chambers, the vane and the housing rotate relatively.
The relative rotational positions of the vane and the housing are controlled by controlling the hydraulic pressure supplied to the hydraulic chambers. By changing the relative rotational phase of the camshaft to the crankshaft, the valve timing is adjusted.
In the above-mentioned valve timing adjusting system, in order to prevent oil leakage from the hydraulic chambers, for example, depressions are formed in the outwardly projecting portions of the vane and the inwardly projecting portions of the housing, and a seal mechanism is provided in each of the depressions. Thus, the seal mechanisms in the outwardly projecting portions of the vane are brought into sliding contact with the inner circumferential surface of the housing, whereas the seal mechanisms in the inwardly projecting portions of the housing are brought into sliding contact with the outer circumferential surface of the vane.
JP-2002-180806-A discloses a seal device to be used in a valve timing adjusting system. The seal device includes a seal member and a plate spring mounted on the seal member. In the seal member, projecting guides provided at both ends thereof are deformed into stopper portions by ultrasonic machining. Thus, the plate spring is mounted on the seal member in a state where both ends of the plate member are held between the stopper portions and a rear surface (opposite to a sealing surface) of the seal member. The plate spring has an arc-shaped central portion and leg portions which are formed parallel to each other at both ends of the central portions.
In JP-2002-180806-A, the stopper portions are formed by ultrasonic machining, and therefore, additional works are necessary to mount the plate spring on the seal member. In addition, when ultrasonic machining is applied to a resin material, a large shape variation may be caused among the stopper portions. The leg portions at both the ends of the plate spring may be warped up when the central portion of the plate spring is pressed, such that the ends of the plate spring contact the stopper portions. Here, since the large shape variation is caused among the stopper portions as mentioned above, a variation in timing of contact between the ends of the plate spring and the stopper portions is also caused. Thus, the spring properties of the plate spring may vary.